Devices for transmitting rotational motions without contact can, for example, be configured as couplings whose function is based on the action of a magnetic field; in drive technology these are designated as magnetic field couplings. These magnetic couplings are used according to the prior art to transmit torques without contact via an air gap and through walls, possibly of hermetically sealed containers. Magnetic couplings are therefore frequently used in flow machines such as gas turbines, for example, but also in fluid pumps. Such a magnetic coupling comprises an outer rotor fitted with magnets in each case, which together with an inner rotor also fitted with magnets is rotationally adjustable about a common axis of rotation. The inner rotor is in this case coupled to a drive shaft, the outer rotor is coupled to a drive shaft or conversely. The desired transmission of the torque from the inner rotor to the outer rotor is accomplished by means of the magnetic interaction of the magnets of the inner rotor with those of the outer rotor.
According to the prior art, for practical manufacturing considerations, conventional magnetic couplings typically use magnetizable or magnetic materials for magnetic field generation, which statically produce the magnetic exciter field required for torque transmission without an electrical current flow being required for this purpose. It is popular to use various ferromagnetic materials such as iron, cobalt or nickel. The use of rare earth metals such as, for example, neodymium alloyed with iron and boron as well as samarium cobalt and samarium iron is also familiar to the relevant person skilled in the art.
Against this background, EP 1 239 572 A2 describes a device for contactless transmission of rotational movements, specifically a magnetic coupling, which has two magnetic coupling members which are mechanically decoupled from one another by a gap. The magnetic coupling members comprise two segmented polarized magnets which are each attached directly to the front-side mutually facing ends of means transmitting the rotational movement.
In conventional magnetic couplings, the effective magnetic coupling of the magnets of the inner rotor with those of the outer rotor proves to be problematical since this depends to a considerable extent on the profile of the magnetic field lines produced by the magnets. In this connection, the person skilled in the art is familiar with different forms of magnetization with which the individual magnets of the two rotors can be provided and which can differ appreciably from one another with regard to the alignment of the field lines of the magnetic field generated by them. In drive technology, magnetic components are usually installed which are characterized by a so-called radial and by a so-called diametric magnetization. Alternatively the use of magnets with lateral magnetization also comes into consideration which is also familiar to the person skilled in the art under the term “Halbach magnetization”.
However, the usual use in the prior art of exclusively one of these three said types of magnetization in a magnetic coupling results in considerable disadvantages in the coupling of motion of the inner rotor to the outer rotor. For example, an exclusive use of magnets with diametric magnetization in the magnetic field produced by the outer rotor results in magnetic field lines which as a result of their orientation relative to the inner rotor contribute only partially to the transmission of torque between the two rotors. This results in a not inconsiderable reduction in the degree of coupling or torque transmission of the magnetic coupling.
It is therefore the object of the invention to provide a device for transmitting rotational motions without contact which is characterized by an improved magnetic coupling. A further object of the invention consists in supplementing a drive system with such a device for transmitting rotational motions without contact.
The said object are solved by the subject matter of the independent patent claim(s). Preferred embodiments are the subject matter of the dependent claims.